<< I've taken her to a vet who says: I could expect surgery to be only 70%
successful in permanently curing this problem because there are several
things that could cause these symptoms (e.g., left, right or both glands,
size of tumor, able to remove entire tumor, etc). At 3 years of age, she is
considered geriatric and I could expect other problems to start occurring."
I don't want to put her through surgery if the odds are she will only gain a
little in longevity.
How long should I expect a female spayed free roaming well fed ferret to
live?
>>

I do not consider a three year old ferret to be geriatric, but rather early
middle-age. I would absolutely not hesitate in taking this ferret into
surgery unless there are other prohibitive problems, such as heart disease.
In that case I would certainly treat with Lupron, as the signs of adrenal
disease are uncomfortable for the ferret. But my first choice in a three
year old ferret would be surgery, hands down. While in there, both glands
can be inspected, both removed if indicated, the pancreas and other organs
can be evaluated. The average life span for ferrets in my practice is seven
to eight years, but I have treated ferrets of up to twelve years old.